google endpoint timeout on devserver - google-app-engine

Question

I am using google-endpoint V2 on app engine standard, with firebase authentication.
When deploying locally, the server starts and runs fine. When a query is issued to access one of the endpointV2, I get an inconsistent behavior:
it works well for a bit (the endpoint returns with the expected payload), but sometimes gets stuck trying to contact https://servicecontrol.googleapis.com/v1/services/my-project-id.appspot.com:check.
It takes about a minute to timeout, then the next query may timeout or return properly...
Any idea of how to resolve that would be appreciated!
The logs in the devserver, for a failed query:
[INFO] GCLOUD: failed because of java.net.SocketTimeoutException: Timeout while fetching: https://servicecontrol.googleapis.com/v1/services/my-project-id.appspot.com:check
[INFO] GCLOUD: Aug 02, 2017 12:27:06 AM com.google.api.control.Client check
[INFO] GCLOUD: SEVERE: direct send of a check request service_name: "my-project-id.appspot.com"
[INFO] GCLOUD: operation {
[INFO] GCLOUD: operation_id: "7453fb02-56e3-48ec-856c-e25d09ccc792"
[INFO] GCLOUD: operation_name: "1.recipes_groceries_appspot_com.ApiadminPop"
[INFO] GCLOUD: consumer_id: "project:my-project-id"
[INFO] GCLOUD: start_time {
[INFO] GCLOUD: seconds: 1501658786
[INFO] GCLOUD: nanos: 76000000
[INFO] GCLOUD: }
[INFO] GCLOUD: end_time {
[INFO] GCLOUD: seconds: 1501658786
[INFO] GCLOUD: nanos: 76000000
[INFO] GCLOUD: }
[INFO] GCLOUD: labels {
[INFO] GCLOUD: key: "servicecontrol.googleapis.com/referer"
[INFO] GCLOUD: value: "http://localhost:4200/_ah/api/static/proxy.html?jsh=m%3B%2F_%2Fscs%2Fapps-static%2F_%2Fjs%2Fk%3Doz.gapi.en.4KxLsUEUJCA.O%2Fm%3D__features__%2Fam%3DAQ%2Frt%3Dj%2Fd%3D1%2Frs%3DAGLTcCOh765ksalVtUgJb_uys4PUTu6HZA"
[INFO] GCLOUD: }
[INFO] GCLOUD: labels {
[INFO] GCLOUD: key: "servicecontrol.googleapis.com/caller_ip"
[INFO] GCLOUD: value: "127.0.0.1"
[INFO] GCLOUD: }
[INFO] GCLOUD: labels {
[INFO] GCLOUD: key: "servicecontrol.googleapis.com/user_agent"
[INFO] GCLOUD: value: "ESP"
[INFO] GCLOUD: }
[INFO] GCLOUD: labels {
[INFO] GCLOUD: key: "servicecontrol.googleapis.com/service_agent"
[INFO] GCLOUD: value: "EF_JAVA/1.0.4"
[INFO] GCLOUD: }
[INFO] GCLOUD: }
[INFO] GCLOUD: failed because of java.net.SocketTimeoutException: Timeout while fetching: https://servicecontrol.googleapis.com/v1/services/my-project-id.appspot.com:check
[INFO] GCLOUD: Aug 02, 2017 12:27:06 AM com.google.api.control.ControlFilter doFilter
[INFO] GCLOUD: WARNING: the check did not succeed; the response null
[INFO] GCLOUD: Aug 02, 2017 12:27:06 AM com.google.api.server.spi.auth.GoogleAppEngineAuthenticator authenticate
[INFO] GCLOUD: INFO: appEngineUser = example#example.com